Pulverizing mill and process of pulverizing material



Oct. 20, 1959 H. HARDINGE 2,909,330

PULVERIZING MILL AND PROCESS OF PULVERIZING MATERIAL Filed Sept. 30. 1954 3 Sheets-Sheet 1 45 i 7 K 42 I) l'. l

BY Wf ATTORNEY Oct. 0. 1959 H. HARDINGE 2,909,330

PULVERIZING MILL AND PROCESS OF PULVERIZING MATERIAL Filed. Sept. 30. 1954 3 Sheets-Sheet 2 28 INVENTOR ATTORNEY Oct. 20, 1959 H. HARDINGE r 2,909,330

PULVERIZING MILL AND PROCESS OF PULVERIZING MATERIAL Filed Sept. 30. 1954 3 Sheets-Sheet 3 INVENTOR H4240: HQQfl/NGE ATTORNEY 2,909,339 Patented Oct. 20, 1959 PULVERIZING MILL AND PROCESS OF PULVERIZING MATERIAL Harlowe Hardinge, York, Pa.

Application September 30, 1954, Serial No. 459,465

14 Claims. (Cl. 241-19) This invention relates to a pulverizing mill and a process of pulverizing material within said mill. More particularly, the invention relates generically to so-called table or disc-roll mills in which rotatable pulverizing or grinding elements are forced by means, other than their own weight, into pulverizing and grinding relationship with a cooperating member in the mill which may constitute a ring, bowl, table or disc, or the like. Such mills usually are employed to grind and pulverize mineral-type material and the process comprising part of the present invention relates to pulverizing this and similar type materials in the various embodiments of mill constructions illustrated and described hereinafter.

While it is not intend-ed to restrict the present invention to the type of mill wherein the material supporting member is rotatably driven about a vertical axis and the cooperating pulverizing rollers are rotated incident to the pulverizing operation of a bed of material fed to the material supporting member, the several embodiments of the invention specifically described hereinafter are suited admirably for use with said type of mill. However, the invention also may be applied to mills in which for example, the pulverizing rollers are positively driven and the material supporting member may or may not be driven, as desired.

In the operation of mills of this type, some type of positive pressure usually is employed to produce greater crushing, grinding or pulverizing of the material between the mill elements which accomplish the same than would mill and, after crushed or reduced by the grinding and pulverizing elements, the desired product usually either progressively spills off or is worked from the extremities of the material supporting member and is collected in a number of different ways, including that of passing a stream of air or other elastic or expansible fluid material through or past the pulverizing Zoneand entraining the desired product or at least some of the desired product in the fluid stream for transfer thereby to other apparatus or a collecting container.

Spring means and particularly compressible coil springs have been used to provide an operating pressure upon the pulverizing rollers of this type of mill for example but this means has the fallacy that, when the pulverizing roller moves away from the material supporting member, for example, the pressure spring will be compressed and the pressure exerted thereby during such functioning of the mill will increase the pressure upon the pulverizing roller and change the characteristics of the mill. Attempts have even been resorted to in such mechanisms to provide counter-acting springs which act against the main pressure providing spring when compressed by movement of the pulverizing roller away from the material supporting member, thereby endeavoring at least partially to lessen the differential in pressure provided by the spring, especially during movements of the pulverizing roller toward {and from the material supporting member, for example.

In none of these prior structures has it been possible to provide a desirable constant or uniform predetermined pressure upon the pulverizing roller, for example, wherelby a substantially uniform pressure would be exerted upon said roller during all reasonable variations in posi tion of the same relative to the material supporting member during the operation of the mill, so that the mill actually has substantially uniform characteristics during all conditions of operation when such is desired.

Further, in mills of the type referred to above which have been in common use, if it is desired to change the pressure upon the pulverizing elements and particularly while the same are acting upon a certain character of material, it usually is necessary to stop the mill in order to vary the pressure between the pulverizing elements to improve the operating efiiciency of the mill or to prevent damage, or not impose an undue burden or overload upon the mill mechanism or the power means driving the same.

Still another inadequacy of conventional mills of the type referred to above is that, when operation of the mill is commenced, the pressure to be exerted upon the pulverizing rollers usually is set initially for a desired amount and then material gradually is fed to the mill until optimum capacities are established. Operation of the mill then usually continues at the present pressure which usually can not be varied during the operation of the mill. If said mill should become overloaded or must be stopped under full load, for example, for any reason, it is then necessary to open the mill and manually remove the excess amount of material therein before the operation of the mill can be resumed. Obviously, this operation entails a considerable loss of time and, sometimes, damage to the components of the mill. Further, in changing certain grinding elements or in making repairs, time is also required to release the compression of springs due to the fact that the springs are adjusted for operating compression, even at no load.

The foregoing inadequacies and undesirable features of existing machines now used have made it desirable to develop particularly some type of pressure providing and adjustment mechanism which would not only result in the mill being easier to operate but would also vastly increase its versatility as to diiferent pulverizing and grinding conditions as well as the range of material upon which the mill is capable of operating and the product resulting therefrom. The present invention provides such type of pressure controlling and adjustment mechanism for the pulverizing elements of a mill of this type.

In the preferred embodiment of the invention, fluid pressure actuated means are employed in several embodiments of mechanism which apply pressure to the pulverizing rollers of a mill of this type and the mechanism is of \such nature that substantially constant, predetermined pressure is applied during all normal operating conditions of the mill, as well as when the pulverizing roller is varied in position due to changing load conditions or otherwise relative to the material supporting member. Further, the pressure control mechanism comprising part of the present invention also is adjustable while the mill is operating, where-by stopping of the mill is not necessary in order to effect such adjustment in pressure when desired.

The present invention also provides in the pressure applying mechanism and the controls therefor, means by which sudden shock movements sustained by the pulverizing elements are absorbed automatically without any substantial increase in pressure or damage to any of the components of the mill.

Another advantage of the present invention resides in the fact that the relative positions of the pulverizing rollers to the supporting member may be varied, while the mill is operating, thereby changing the pulverizing and discharging characteristics of the mill, and a current of air or other elastic fluid is directed either through or past the pulverizing zone so as to engage the discharge from the pulverizing zone and entrain a desired range of sizes of product particles and remove the same from the mill, said fluid current being regulatable relative to the discharge conditions from the pulverizing area of the mill to permit the entrainment of a rather wide selected range of sizes of product particles and particularly the finer sizes of such material.

Still another advantage of the invention relative to that described immediately above resides in the fact that classifying mechanism, operated in conjunction with the stream or current of expansible or elastic fluid which entrains the product particles, may be operated and adjusted so as further to classify or separate, for example, some of the larger particles of the entrained product from the exiting stream and return the same to the mill for further pulverizing while the finer sizes of a desired range continue to be removed from the classifier for further operation or storage.

In several of the embodiments of the invention, it has been found that pneumatic pressure admirably is suited to achieve the desired results of the invention, while in other embodiments thereof, hydraulic pressure is used in conjunction with pneumatic pressure to achieve beneficial and desired results with the invention.

Details of the foregoing advantages and objects of the invention and of the several embodiments of structure incorporating the same, as well as the method of pulverizing which is possible to achieve with said structural embodiments of the invention, are set forth in the following specification and illustrated in the accompanying drawings comprising a part thereof.

In the drawings:

Fig. 1 is a vertical sectional side elevation of an exemplary mill embodying the principles of the present invention.

Fig. 2 is an exterior side elevation of the mill shown in Fig. 1 but as seen at 90 to the elevation shown in Fig. 1.

Fig. 3 is an enlarged fragmentary, vertical sectional elevation of the mill shown in Fig. 1.

Fig. 4 is an enlarged fragmentary detail, partly in vertical section, of one position of the pulverizing elements during operation of the mill.

Fig. 5 is a view similar to Fig. 4 but showing the pulverizing elements in different relative positions to those shown in Fig. 4.

Fig. 6 is a fragmentary elevation, partly in vertical section, of another embodiment of pulverizing mill embodying the principles of the present invention.

Fig. 7 is a side elevation, mostly in vertical section, of still another embodiment of pulverizing mill incorporating the principles of the present invention.

Fig. 8 is a fragmentary side elevation showing details of pressure control mechanism constituting a further embodiment of that portion of the invention.

Fig. 9 is a top plan view, partly in section, taken on the line 9-9 of Fig. 8, and illustrating the control mechanism shown therein.

Fig. 10 is a fragmentary side elevation, partly in section, of still another embodiment of pressure control mechanism of the invention.

Fig. 11 is a fragmentary side elevation, partly in section, of still another embodiment of control mechanism for the invention.

In the foregoing figures, various embodiments of the present invention have been illustrated in selected exemplary constructions of a pulverizing mill, which best show the advantages of the invention structurally, as well as may be incorporated in other types of mills to which such I principles are applicable.

Referring to the drawings, and particularly Figs. 1 through 3, the mill shown therein comprises a base 10 and an enclosing casing 12 extends upwardly therefrom and also encloses a classifying unit 14. A product exhaust conduit 16 communicates with and extends outward from the upper portion of casing 12, above the classifying unit 14. Any appropriate type of material inlet or feed 18 is provided in the casing 12, as shown in Fig. 2, and discharge outlets 20 also are provided for tramp particles or other foreign material which is undesirable in the product to exit from the mill through said outlets.

A gear reduction unit 22 is stationarily mounted within a suitable compartment provided therefor in the base 10, this being covered by a suitable deflector and seal 24 which, preferably, is annular-and extends inward and upward as clearly shown in Figs. 1 and 3. Arranged centrally on the top of the gear reduction unit 22 is a rotatable member 26 to which a preferably circular material supporting member 28 is attached by conventional means. The specific illustration shows a disc-like member but this merely is exemplary since other shapes of supporting members may be used in accordance with the principles of the invention. In accordance with usual practice, the material supporting member 28 is provided with an annular groove on the upper face thereof which receives an annular, wear-resisting grinding face member or disc 30. Said disc also is held in fixed relationship to the supporting member 28 by suitable conventional clamping means, whereby the disc 30 rotates in unison with the supporting member 28. Power to rotate the material supporting member 28 is provided by any suitable motor 32 which drives the gear reduction mechanism 22.

In the specific embodiment of the mechanism illustrated in Figs. 1 through 5, a pair of rotatably mounted grinding rollers 34 are provided. Supporting means for these rollers constitutes a pair of arms 36 which are pivotally supported at their lower end by heavy journals 38 carried by bearings fixed relative to the base 10 of the mill. The axes of the journals 38 are substantially horizontal and parallel to each other. Short, heavy shafts 40 respectively project transversely from and are fixed to the arms 36, intermediately of the ends of the latter. As shown in section in the left-hand side of Fig. 1, suitable roll or ball bearing units rotatably support the pulverizing rollers 34 on the inner ends of the shafts 40. The axes of the shafts 40 are fixed relative to the arms 36.

The upper or outer ends of the arms 36 are provided with cross members 42 which are fixed thereto and the outer ends of the cross members project beyond the sides of the casing 12 as clearly shown in Fig. 2. A pair of arm positioning units 44, each comprising a cylinder 46 and a relatively reciprocable piston 48 and piston rod 50, respectively connect the opposite ends of the cross members 42 as clearly shown in Figs. 1 through 3. Thus, it will be seen that such positioning of the outer ends of the arms 36 permit either independent or simultaneous movements of the pulverizing rollers 34 relative to member 30 and each other, at least within certain limits.

Positioning of the pulverizing. rollers 34 relative to the material supporting member 28 and particularly the face member or disc 30 thereof, is accomplished by varying simultaneously the pistons 48 relative to the cylinders 46 in the positioning units 44. This is accomplished by fluid pressure means, one embodiment of which is illustrated in Fig. 2 and constitutes a pump 52 which is ftiriven by a pair of pulleys and a belt interconnected to the drive shaft of motor 32. However, if desired, a separate motor may be used. Also, if pneumatic fluid is to be used, the pump 52 may comprise a small air compressor. In either event, fluid under pressure passes through valve 54, by which the fluid system may be shut off, if desired, and from there to a pressure regulating valve 56 which is settable to any pressure desired within "a reasonable range. Said valve may be adjusted, even while the mill is operating. The principal purpose of the valve 56 is to deliver a predetermined fluid pressure unidirectionally to the conduit 58 which leads to the cylinders 46 of the arm positioning units 44. It will be seen that the conduit 58 extends commonly to both of the cylinders 46. Usually the pump or compressor .52 will deliver a greater pressure than required by the setting of the valve '56, but said valve insures delivery of only a desired predetermined pressure for which the valve is set.

A bleeder or regulating valve 60, whichever is prezferred, also is connected to the conduit 58 and a pres- :sure gauge 62 likewise is connected to said conduit so as visually to indicate at all times the pressure existing within said conduit.

It will be seen that the arm positioning units 44 respectively are disposed at opposite sides of the casing 12 and they, like the arms 36, are mounted exteriorly of the casing, whereby they readily are accessible to any rservicing which may be required and, also, in noway interfere with the passage of finished product upward through the mill casing 12, particularly while being rernoved from the mill by means to be explained herein- :after. Inasmuch as it is contemplated that the arms 36 and shafts 40 which are supported thereby will move relative to casing 12, and in order to prevent the escape of pulverized or other material within the mill during such movement of the arms and shafts, suitable sealing members 64, either slidacle or flexible, are provided between the shafts 4t) and the walls of the casing 12 through which the shafts extend, as clearly shown in Fig. 3 particularly.

The operation of the pulverizing portion of the mill illustrated in Figs. 1 through 5 now will be described. Raw material such, for example, as mineral ore, to be pulverized is introduced through the inlet 18, preferably at a constant rate, by any suitable means, not described. Said material discharges onto the disc 36 which either is rotatingat the time, or the rotation thereof may be commenced after some material has been introduced to the disc 30. The pressure and/or position of the pulverizing rollers 34 relative to disc 30 then is adjusted by regulating the valve 56.

Depending upon the type of material being operated upon, the fineness of the product desired, the rate of feed of the raw material, the height of the dam 70, as well as other factors, different thicknesses of beds of material 66 may be required or desired. Usually the dam 70, which is annular, projects above the face of member 30 and is adjustable in height by regulation of means such as a series of circumferentially spaced bolts 71. Such change in height is possible by usual means and constitutes a major change which, in any event requires stopping the mill, but is one means of changing the thickness in the bed of material. Two diflerent examples of such beds are illustrated respectively in Figs. 4

and 5. Thus, the spacing of the rollers 34 relative to the disc 36, generally, is critical and a desired control of such space is possible with the present invention so that a desired spacing is obtained and automatically maintained, simply by regulating valve 56, assuming other factors remain substantially constant. It will of course be understood that if no pressure exists in cylinders 46, and with no material on the disc, the weight of the rolliers 34*will position them by gravity against the disc 30 or against stops provided but not shown to keep the rollas shown in Fig. 3.

ers just clear of the disc. After operation of the mill is commenced and material flows onto the disc, regulation of valve 56 usually must take place and one of the beneficial advantages of the present invention is that such regulation may be. made while the mill is operating. In view of the interconnection of the upper ends of arms 36 by the positioning units 44, adjustment of the spacings ofboth rollers 34 relative to disc 30 takes place simultaneously and evenly. That is, the pressure exerted by both rollers will be uniform as is also the pressure on both sides of arms 36 and journals 38.

After the desired setting of valve 56 is achieved, so that a desired pressure upon and spacing between the rollers 34 and disc 30 results, such pressure will remain uniform during continued'operation of the mill, especially under normal conditions. Assume, however, that the feed of raw material to the mill varies and is increased for any reason, for example, whereby the thickness of the bed 66 upon disc 30 increases, such increase will move the upper ends of arms 36 apart and place the fluid in the piston 46 under increased pressure, which, in turn, is imparted to the pulverizing rollers 34. In order that the pressure of the rollers 34 may be maintained substantially at the predetermined desired pressure for which the valve 56 is set, even though the thickness of bed 66 increases, such excess pressure is relieved by valve 60 as it occurs.

Assuming further that valve 60 is a regulating valve and has been set to relieve or discharge pressure in excess of that provided by control valve '56, then, under such circumstances, the excess pressure will be discharged to atmosphere, especially where the pressure fluid is pneumatic. However, assuming that valve 60 is a bleeder type with a relatively small discharge opening which constantly discharges a small amount of fluid, such bleeding characteristic of valve 60 then will dissipate the excess pressure occasioned by the increase in the thickness of bed 66, referred to above, and the constant pressure supplied by regulating valve 56 will maintain the required amount of pressure in the conduit 58 and cylinders 46 after such bleeding has dissipated the excess pressure occasioned by the increase in bed thickness. All of the foregoing takes place automatically and requires no attention from the operator.

Under other circumstances such as when some foreign substance as a piece of tramp iron 68, shown in Fig. 3, occurs in the material fed to the mill, when the roller 34 encounters such a lump of hard material of this type,

a shock is sustained by the mill in the nature of suddenly elevating the rollers 34 engaging said lump of material This results in a sudden increase in pressure within the cylinder 46 of each of the positioning units 44 but, under the circumstances of using pneumatic or other elastic fluid within said cylinders, the compressible nature of such fluid will minimize said shock and permit the rollers to pass over the obstruction without creating undue stresses and injury to the compoents of the mill, especially if said movement is of considerable magnitude. Again, where the increase in pressure is due to a sudden increase in feed size or quantity and is sustained for a period of time, the above described operation of .valve 60 will take place and relieve the mill of the increase in pressures and return the pressure to normal in a short time. Such operation also will be automatic and needs no attention from an operator. The mill is protected from undue shock and continued operation is assured at the desired constant rate of pressure ing the mill.

"7 hence there is notendency for exerting an unbalanced pressure on the journals 38.

Once the mill is operating and the desired pressure required by the setting of regulating valve 56 has been developed by pump or compressor 52 and is being exerted by the positioning units 44 against the rollers 34, the

action of the positioning units 44 then becomes essentially a holding action. When air is used as the fluid in the pressure system, little additional air, if any, will be taken into the system during such holding operation of the positioning units 44. At most, only enough will be taken in to compensate for the leakage through valve 60 if the same is of the bleeder type. Thus, a very small compressor 52 is all that will be required to maintain suitable pressure upon the puverizing rollers 34. The power consumed to actuate such compressor is nominal.

Even though it may be possible to obtain a source of air from other means in a plant, for example, there is an advantage in having the compressor coupled to the power means 32 for the mill, not only to insure continuity of operation but, when the mill has been shut down and the air pressure released, a lapse of time will be required to build up the air pressure when next start- This arrangement insures lower power consumption under these circumstances, when starting up the mill. Of even greater importance is when the mill has been stopped under a loaded or overloaded condition. Then, if all pressure is removed from the rollers, the mill can be started without overloading the mill motor and then as the material on the disc is gradually reduced under these conditions, the pressure can then be gradually brought up to normal. It is not necessary in this situation manually to remove the load of material in the mill before it can again be started as now is required with conventional mills and especially those utilizing springs to provide the pressure for the pulverizing rollers.

Referring now to Figs. 4 and 5, wherein two diiferent depths of beds 66 of materials are illustrated, it will be understood that optimum conditions may be obtained at either bed depth, or others, depending upon the nature of the materials being pulverized, the condition and nature of the operation, as Well as fineness of product desired. Hence, for-optimum results, it is desirable that the position of the rollers 34 may be varied relative to disc 30 within a reasonably wide range in order that operation of the rollers upon different desired thicknesses of beds of material may take place. For example, but

without restriction thereto, when pulverizing a relativelyfine feed of material or when a very fine product is desired, it may be best to operate the mill with a low or relatively thin bed depth as illustrated in Fig. 4, as opposed to grinding a coarser material to a lesser degree of fineness where a greater depth, as shown in Fig. 5, may prove to be superior.

The etfect of the height of the so-called dam 70, constituting the perimeter of material supporting member 28, also sometimes is an important feature in this type of mill. Such dam height, on occasions is changed, by trial and error, to obtain the best bed depth. However, the present invention, particularly where the roller may be maintained at various heights, as desired, largely will obviate any need to change the desired height of the dam .70 by trial and error means or otherwise.

The height of the dam 70 relative to the position of the roller 34 above the disc 30 has great effect upon controlling, for example, the angle at which the material leaves or is discharged from the disc 30. Note, for example, in Fig. 4, the discharging material 72 assumes a path which is substantially more vertical than the path of the material 74 in Fig. 5, wherein the roller 34 is spaced farther from the disc 30. This angle of exiting or discharging material is of particular importance when said discharge material is entrained in an upwardly directed stream of elastic fluid 76, for example. The ability to change the roller pressure at will and while the mill is running contributes greatly to increased efficiency of operation by virtue of its efiect upon bed depth such as the change in degree of plowing and embedding action of the rollers 34 in the bed of material 66.

Streams of elastic fluid 76, such as air, may be introduced into casing 12 through any suitable inlet ports such as openings 78 near base 10. It will be understood that these openings may communicate with conduits constituting part of the closed circuit mill and classifying assembly which will include a fan or blower. Such closed systems are commonly used and the present illustration will not be burdened with a showing thereof. However, it will be understood that the stream 76 of elastic fluid will enter the lower portion of casing 12 and move upwardly past the pulverizing zone so as to intersect the respective discharged material 72 or 74 in Figs. 4 and 5, for example, and entrain in said streams of fluid a range of sizes of pulverized material. This will be carried upward into the upper portion of casing 12 wherein classifying unit 14 is operated.

It is intended that the specific showing of classifying unit 14 only be exemplary and the same may comprise a rotatable member having thereon a series of circumferentially spaced vanes 80. The member includes a shaft 82 which is supported rotatably by the upper portion of casing 12 and is driven by any suitable means such as a pulley 84, connected to a motor, not shown. This specifically illustrated classifier operates upon the principle of the vanes engaging the particle-laden fluid current 76, indicated by arrows in the various figures, and the vanes 80 will hit at least the larger particles of material within said fluid streams and impinge them against the sloping sides 86 of casing 12, and cause the same to slide down such sides and re-enter the pulverizing zone for further action by the pu1veriz- 'mg members. The speed at which the rotating member rotates may be varied so as to cause ditierent sizes of particles to be removed from the stream 76, whereby, for example, fine particles of a predetermined range of sizes will be removed from casing 12 through exhaust conduit 16. From there it will be carried to further treating apparatus or storage.

It will be seen particularly from Figs. 4 and 5, in th light of the above description of the operation of the streams of elastic fluid 76, that the angularity of the discharge material 72 and 74 in these figures will have considerable bearing upon the quantity and sizes of particles of material which will become entrained in said stream of fluid 76, whereby the position of the pulverizing rollers 34 relative to the material supporting disc 30 is critical, yet the mechanism comprising the present invention serves to hold said rollers at a desired spacing from the disc 36 when the desired spacing has been ascertained following initial testing under the particular conditions existing at the time. Regulation of such spacing easily is achieved by varying the setting of regulating valve 56, even while the mill is operating. Such adjustment takes place at no risk or danger to the mill or operator and the operator can quickly and easily bring the mill up to its best grinding condition with a minimum of loss of time and spoiled product. It is impossible so to operate and adjust a spring loaded roller.

Another embodiment of mill incorporating the principles of the present invention is illustrated in sectional elevation in Fig. 6, wherein the material supporting member 28 is of the so-called bowl type and has somewhat vertically extending sides 88 which support a frustoconical wear ring 90 with which a plurality of so-called conical pulverizing rollers 92 cooperate. In this embodiment of the invention, the casing 12 also includes substantially horizontal, annular plate portions 94 which support the plurality of roller assemblies now to be described.

As distinguished from the mountings for rollers34 in the embodiment of the invention shown in Figs. 1 through 5, the embodiment shown in Fig. 6 illustrates three exemplary rollers 92, each of which are rotatably supported by bearing sleeves 96 which are pivotally connected, adjacent their upper ends, to journals 98. Rigidly connected to the sleeves 96 and extending outward there from, in cantilever fashion, are pressure arms 100 which move with the sleeves 96 about the axes of the journals 98.

Each of the mounted roller units includes a positioning unit constituting a cylinder 102 within which a piston 104 is reciprocable. The upper ends of the piston rods 106 are pivotally connected to the outer ends of pressure arms 100 and the fluid pressure supplying means for this embodiment of mill is similar to that shown in Fig. 2, for example, for the previously described embodiment of the invention. The cylinder 102 of each of the units is commonly connected to a supply conduit 58, whereby all of the pulverizing rollers 92 will be moved simultaneously in unison, yet especially when the fluid pressure is pneumatic, the supporting arrangement for each of the pulverizing rollers 92 is such that they may move independently of each other, especially to absorb individual shocks imposed upon any roller 92, as when a piece of tramp iron is engaged by the roller, for example. The principal'difference between this embodiment of the invention and the previously described embodiment is that the mill shown in Fig. 6 is of the so-called bowl type, yet the principles of the invention equally are applicable to said bowl type as well as the disc type shown in Figs. 1 through 5. The same reference numerals are given the elements of the pressure supplying arrangement in Fig. 6 as in Fig. 2, inasmuch as the same operates similarly. Further, the exemplary classifying unit 14 shown in Fig. 6 operates similarly to that shown in Fig. 1.

Fig. 7 illustrates another embodiment of mill to which the principles of the present invention are applicable. in this embodiment, a material supporting member 108 is supported rotatably by the base 10 and driven by any suitable power means;- The upper face of the material supporting member is somewhat flatly conical, as shown in Fig. 7, and slopes downwardly from the center toward the perimeter thereof. An annular concave groove 110 also is provided near the periphery of member 108 for the reception of a series of rotatable pulverizing members such as balls 112.

An annular pressure member 114, having an annular concave groove 116 in the lower face thereof engages the upper surfaces of the rotatable members 112 and a sufl'icrent number of members 112 is placed between the members 108 and 114 that ample crushing effect is provided by said rotatable members when the member 108 is rotated while the pressure member 114 is held suitably against movement about the vertical axis of the mill.

Raw material to be pulverized is introduced into the casing 12 through chute 118 and falls into the pulverizing zone adjacent the periphery of member 108. Pressure upon the rotatable members 112 is caused by member 114 which in turn is placed under pressure by a plurality of pressure units 120, preferably at least three in number and circumferentially spaced evenly around member 114, and comprising cylinder and piston units clearly illustrated in Fig. 7. The cylinders of said units are all connected by flexible, pressure conduits commonly to conduit 58 and, otherwise, the pressure control and regulating mechanism illustrated in Fig. 7 is similar to that shown in Figs. 2 and 6, similar reference numerals for the components being indicated in all figures.

One of the principal advantages of the type of mill shown in Fig. 7 is that it is a so-oalled ball-type pulverizing mill but the structure is such that uniform pressure will be exerted at all times upon all of the rotatable '10 members 112 and no uneven wear of the pressure mm: ber 114, rotatable members 112, or material supporting member 108 will take place in view of the even pressure afforded by the plurality of pressure units which are commonly and simultaneously under the same pressure.

Air, for example, may be introduced to this mill through a suitable inlet 122, so that an elastic fluid stream is provided which will entrain and carry a desired range of pulverized product into contact with the classifying unit 14 for the purposes described above relative to the several embodiments referred to in detail therein.

The importance of being able to maintain constant pressure at different bed depths has been referred to hereinabove and described relative to the various illustrations and examples. However, it also is well known in the art that grinding and pulverizing mills, and particularly mills of this character as illustrated herein, are subjectto many variables, and in order to operate them at maximum efliciency, it is desirable, but seldom possible to make adjustments or changes readily. Thus, optimum conditions seldom are arrived at or, if once obtained, a slight change in condition may decrease the efficiency of the mill which could otherwise be brought back to normal by the use of suitable adjustments if it were possible to make such adjustments. Under these circumstances, it sometimes is desirable to vary the pressure upon the pulverizing rollers in such a manner that the pressure will increase to desired degrees as the load upon the material supporting member increases. Figs. 8 and 9, respectively in side and plan views, illustrate one exemplary type of mechanism applicable to the embodiments illustrated and described hereinabove, and especially the embodiment shown in Figs. 1 through 5 for making such an operation possible. In Fig. 8 for example, only the upper end of the arms 36 are shown. In accordance with the invention, the regulating valve 56 is interconnectedto one of the arms 36 so that, as the load or bed of material 66 increases upon the disc 30 for example, the upper ends of the arms 36 will progressively move away from each other. Such movement is utilized to vary the setting of regulating valve 56 gradually so as to increase the pressure supplied to cylinder 46 and imposed upon pulverizing rollers 34. Conversely, of course, if desired, by connecting the valve and arm so that the above action moves the valve in closing direction, this arrangement may be used to decrease the pressure progressively.

Exemplary mechanism illustrated in Figs. 8 and 9 accomplishes such adjustment for increasing the pressure upon an increasing depth of bed and comprises a preferably slotted arm 124 which projects radially outward from the operating stem of valve 56 and an adjustable link 126, having a turn buckle 128, for example, therein connects the valve operating arm 124 to one of the arms 36, as clearly shown in these figures. By such arrangement, the starting position for the adjustment of valve 56 taking place may be regulated by varying the length of link 126, while the amount of opening of the valve 56, in relation to the movement of the upper end of arm 36, may be varied by the adjustable positioning of the connection for link 126 in the slot of arm 124. A number of variable positions of the link 126 are shown in dotted lines in Fig. 9 and it will be understood that this arrangement affords rather wide latitude in varying the increase in pressure to the pressure system for the pulverizing rolls 34 when it is desired to increase such pressure upon an increase in the load of material upon the material supporting member 28. If it is desired to decrease the pressure under similar circumstances, the arm 124 may be disposed at to the position shown in these figures.

Under circumstances where hydraulic fluid is used as the medium for producing the pressure upon the pulver- -izing rollers 34, it will be understood that the same is supplied to the cylinder 46 of the positiomng unit 44 shown in Fig. 10. The use of hydraulic liquid for this purpose is satisfactory, especially where either no foreign or tramp material will be encountered in the mill. Under these circumstances, a very small hydraulic pump, such as pump 52, shown in Fig. 2, is all that is required in the arm positioning mechanism which, in effect, will be required only to produce a holding action for the rollers 34. Under normal operating conditions, the movement of the piston within the cylinder 44 will be nominal except for changes in conditions in the material in the mill, in which event the action of changing the pressure upon the rollers 34 by discharging excess pressure through valve 60 of the various systems described and illustrated hereinabove could take place so as to reestablish a constant pressure condition in any new set of conditions existing within the mill at the time.

Thus, the benefits of the present invention may be achieved while using a hydraulic fluid for the pressure medium. However, in normal mill operation, foreign material such as tramp iron frequently will enter the mill and using the simple hydraulic system referred to above, operating primarily as a pressure holding arrangement, would be impractical unless some means for absorbing sudden shocks such as when one of the pulverizing rollers engages a piece of tramp iron, were provided. This is due to the fact that the flow of oil or some other non-compressible liquid usually would be too slow to permit movement of the roller 34 sufficiently rapidly enough from the material supporting member so as to prevent damage to the mechanism,

In Fig. 10, additional means are provided by which said sudden shocks may be sustained by the mill without injury thereto. It will be understood that this illustration is merely exemplary of one type of shock absorbing mechanism which may be used and comprises, for example, extending the piston rod 50 through one of the arms 36 a suflicient distance to enable the use of a compressible spring 130 which surrounds the piston rod 50 and an adjustable holding collar and nut 132 may be threaded onto the outer end of piston rod 50. The pressure exerted by spring 139 will of course be regulated so that it will be possible for the spring to absorb sudden shock movements of either of the arms 36, depending upon which of the rollers 34 engages a piece of tramp iron for example, and although such shock will increase the pressure upon the pulverizing roller 34, such increase will only be momentary and then the holding pressure afforded by unit 44 will be restored to normal after the foreign material has been passed by the roller 34. It will be understood of course that if the mechanism illustrated in Fig. is used, it will be applied to all of the holding units 34 employed in the mill.

Still another embodiment of roller positioning and pressure providing means comprising a combination hydraulically operated pressure holding unit and compressible fluid shock absorbing means is illustrated in Fig. 11. In this figure, only the fragmentary upper ends of the arms 36 are shown, the same being interconnected by a cylinder and piston unit 44 for positioning the arms and compression rollers supported thereby. The cylinder communicates with conduit 58 which also is connected to a pressure reservoir tank 134 which, preferably, has a substantially larger volume than that of cylinder 46.

The system shown in Fig. 11 also includes a storage tank 136 which contains a supply of hydraulic fluid, and a hydraulic pump 138 pumps fluid from the tank 136 to a regulating valve 140 which is settable to discharge or transmit hydraulic fluid at various desired predetermined pressures only. This pressure may be varied to suit a desired pressure condition within the cylinder 46. Hydraulic fluid discharged from valve 140 enters the reservoir tank 13 through conduit 135 and compresses the elastic fluid therein, air for example, and in turn such elastic fluid is compressed within the cylinder 46 and exerts pressure upon piston 48.

It is to be understood thatthe system illustrated in Fig. 11 primarily is exemplary and details thereof may be varied to suit various conditions of operation of the mill. Some suitable type of pressure gauge or visual indicating means 142 preferably is provided. An electrical circuit 144, connected to a source of current, furnishes current to the electric motor 146 which operates pump 138. The pump 138 normally delivers hydraulic fluid at a pressure in excess of any contemplated setting of valve 140. Initially, the pump is started by closing switch 147 which not only may be a manually operated circuit control switch to start and stop the motor but also preferably is pressure actuated and thus is operable automatically in response to variably settable upper and lower pressure limits periodically to start and stop motor 146, as hydraulic supply under pressure is required by the system.

A compression dome 149 is connected to valve to maintain excess pressure provided by pump 138 constantly to valve 140, which is a one-way valve, until such excess pressure is reduced substantially to that for which the valve 140 is set, thereby minimizing operation of motor 146 and the pump 138 and switch 147. Preferably, a bleeder valve 150, having a relatively small opening, will gradually discharge fluid through conduit 148 to storage tank 136, upon which a sight gauge 152 may be provided. This gradually dissipates excess pressure occurring upon piston 48 as when the rollers 34 move away from disc 30 due to increase in the material feed, for example, thereby restoring the pressure upon rollers 34 to predetermined normal as in regard to the other embodiments of the invention described above. That is, valve functions similarly to valve 60 in Figs. 2 and 6 through 8. Thus, in effect, hydraulic fluid holds the rollers 34 at normal predetermined pressure while the elastic fluid'in cylinder 46 and tank 134 readily absorbs and cushions sudden shock movements of the rollers as when lumps of tramp iron are encountered.

The pump and pressure control system described and illustrated relative to Fig. 11 also may be used with pneumatic fluid, if desired, but under such circumstances the storage tank 136 and reservoir 134 would be unneccessary as when air is used, the pump could draw from atmosphere and valve 150 would discharge to atmosphere. The compression dome 149 however would be desirable in such an arrangement.

The only pump required in the system shown in Fig. 11 is hydraulic pump 138 and this may be of relatively small capacity, smaller than that required in an entirely pneumatic pressure control system. Further, in general, higher pressures may be generated by the system shown in Fig. 11 than in an entirely pneumatic system of similar capacity and these advantages are'obtained by the use of a relatively simple system which requires substantially no maintenance and yet the desired pressure within the arm positioning units 44 may readily be varied, especially while the mill is operating, by changing the setting of valve 140.

From the foregoing, it will be seen that the various embodiments of the invention illustrated and described herein afford pressure regulation for the pulverizing rollers which automatically maintains a desired and equal pressure upon such rollers during all normal operation of a pulverizing mill, as well as afiording a combination pressure holding and shock absorbing mechanism which automatically absorbs shock movements of any of the pulverizing rollers as when hard foreign substances such as tramp iron lumps are encountered by the pulverizing rollers, all without damage or injury to any of the components of the mill.

One of the salient advantages of the arrangement afforded by the present invention is that the position of the pulverizing rollers relative to the material supporting member may be varied in accordance with load or other operating requirements and conditions, while the mill is operating. Also, even though the rollers are varied in pos tion relative to the material supporting member during operating conditions, the pressure thereon still is maintained constant at substantially the desired, preset amount of pressure. Such variation of the position of the rollers and the maintenance of the constant predetermined pressure is accomplished automatically. Further, another advantage comprises the ability to vary the pressure, while the mill is operating, if such variatron and pressure is desired to provide difierent operatmg conditions.

The pressure providing and control arrangements provided by the invention also permit the ready release or reduction of the pressure upon the pulverizing rollers, especially when the operation of the mill is commenced with a load of material within the mill, such as after the mill has been shut down for any purpose. Such variation or reduction in pressure readily is achieved simply by varying the setting of a regulating valve, while the mill is operating or not. After the operation of the mill has been started, the pressure may be varied, while the mill is in operation, to exert a desired pressure upon the pulverizing rollers in accordance with the load of the material being processed by the mill and the type and quantity of product desired. Such adjustment of the rollers also permits the varying of the spacing between the pulverizing rollers and the material supporting disc or pan for example, whereby the direction of the discharged material may be controlled in relation to a variable elastic fluid which moves past or through the pulverizing zone so as to entrain therein a desired range of sizes of particles of pulverized material.

This invention also makes it possible to control automatically the rate of change of pressure on the rolls as the rolls move away from or toward the other pulverizing element if such rate of change is desired.

Concerning wear upon the rollers 34 or the material supporting member, the diameter of the rollers usually is less than the length of the supporting arms 36, for example. Hence, wear upon the rollers or material supporting member will result in an increased movement of the outer ends of the supporting arms 36. In mills used at present which employ springs to provide pressure upon the pulverizing rollers, it will be appreciated that such increased movement of the supporting arms will result in the tension of the springs decreasing rapidly, the operation of the mill being affected to the same degree in various ways such as by not pulverizing the product to the degree of fineness desired or possibly permitting the thickness of the load bed upon the supporting member increasing to an undesirable amount with consequent results.

In contrast to the foregoing, the utilization of pressure producing and regulating means such as described and illustrated in the present invention, wherein piston and cylinder units are actuated and controlled by fluid pressure positioning means which control the pulverizing rollers, the control mechanism of the present invention maintains the pulverizing rollers under substantially constant predetermined pressure at all times and will compensate automatically for the wear upon the pulverizing rollers ormaterial supporting member. Simply by providing a piston rod and cylinder of suitable length, very substantial adjustability of the position of the pulverizing rollers relative to the material supporting member is possible, as well as permitting substantial Wear in the rollers and automatic compensation therefor.

In all of the various embodiments of the invention and particularly the pressure controlling mechanism for pulverizing mills of the character described, the control mechanism is relatively simple, as well as easy and inexpensive to maintain, and adjustment in the pressure upon the pulverizing members requires only the operatiori of a valve, which may be regulated in setting either when the mill is idle and especially while operating. Thus, stopping of the mill is not necessary when a change in pressure is required or desired, as is necessary in mills which, for example, utilize springs to maintain the pressure upon the pulverizing elements. Further, conventional mills of the type illustrated and described herein, at present, utilize springs in various arrangements to produce and maintain the required pressure upon the pulverizing elements of the mill. In many instances also, the cost of such spring arrangements has been found to be greater than the mechanism provided by the present invention.

The ready accessibility of the pressure producing and controlling elements of the present invention also represents an advantage over existing mills in use at present, particularly when repair and replacement of any of the components is required.

Further, while'the foregoing description of the invention includes the use of a stream of elastic fluid to entrain the products of the pulverizing zone of the mill, and classifying means acting upon said entrained product, it is to be understood that the pulverizing portion of the mill may be used without these additional features, if desired.

While the invention has been shown and illustrated in its several preferred embodiments, and has included certain details, it should be understood that the invention is not to be limited to the precise details herein illustrated and described since the same may be carried out in other ways falling within the scope of the invention as claimed.

I claim:

1. A mill of the continuously pulverizing type comprising in combination, a casing having an inlet, a substantially horizontal material supporting member rotatable within said casing about a substantially vertical axis and positioned to receive material continuously from said inlet, said supporting member being arranged to maintain thereupon a desired depth of material being pulverized and from the periphery of which pulverized material of a desired range of sizes is discharged, a pulverizing member supported for rotation, means supporting said pulverizing member rotatably above said supporting member in position to dispose the peripheral surface of said pulverizing member in opposition to the material supporting surface of said material supporting member to effect continuous pulverizing of material fed between said surfaces, power driving means interconnected to one of said members and operable to rotate it at a desired speed and thereby driving the other member, fluid operated holding and shock absorbing means interconnected to said pulverizing member and supporting means therefor and operable to permit said pulverizing member yieldably to move away from said supporting member to accommodate various thicknesses of the bed of material upon said supporting member while said material is being pulverized, means interconnected to and operable to furnish a supply of fluid under pressure to said holding and shock absorbing means, selectively settable control means connected between said supply means and said holding and shock absorbing means and operable to regulate the flow of fluid to said latter means to furnish pressure thereto slightly in excess of a desired predetermined operative pressure upon said pulverizing member, and regulating means connected to said control means and operable to maintain the fluid pressure upon said holding and shock absorbing means at said lesser desired predetermined operative amount, whereby said pulverizing member exerts said predetermined pressure upon the material being pulverized regardless of the thickness of the bed thereof upon said supporting member.

2. A mill of the continuously pulverizing type comprising a casing having an inlet opening, a material supporting member rotatable within a substantially hori 15 zontal plane within said casing about a substantially verticalaxis and positioned to receive substantially continuously fromsaid inlet material to be pulverized, power driving means interconnected to said member and operable to rotate it at a desired rate of speed, a pulverizing roller rotatably mounted above said member, and supporting means for said'roller operable to position the peripheral surface of said roller a variable distance above the material supporting surface of said member to effect pulverizing of material between said surfaces as said member is rotated, in combination with pneumatic fluid pressure operated holding and shock absorbing means interconnected to said supporting means and comprising a pneumatic pump, a one-way regulating valve connected to the outlet of said pump and settable to deliver a desired predetermined pressure, a cylinder and piston unit connected to said roller supoprting means, a conduit connected between the pressure end of said cylinder and outlet end of said regulating valve, and a control valve connected in said conduit between said cylinder and regulating valve operable constantly to bleed a predetermined amount of pneumatic pressure from said cylinder less than the pressure for which said regulating valve is set, said bleed valve being adjustable to bleed pneumatic pressure fluid of a desired amount therefrom as required by the material being pulverized, whereby said roller may move away from said member as required by grinding conditions while having substantially the same pressure exerted thereupon at all operable spacings between said roller and member as pulverizing takes place, said pressure regulating valve also being variable as desired while said mill is operating to vary the pressure exerted by said pulverizing roller.

3. A mill of the continuously pulverizing type comprising in combination, a casing having an inlet opening, a substantially horizontal material supporting member rotatable within said casing about a substantially vertical axis and positioned to receive material continuously from said inlet opening, said supporting member being arranged to maintain thereupon a desired depth of material being pulverized and from the periphery of which pulverized material of a desired range of sizes is discharged, a pulverizing member supported for rotation, means supporting said pulverizing member rotatably above said supporting member in position to dispose the peripheral surface of said pulverizing member in opposition to the material supporting surface of said supporting member to effect continuous pulverizing of material fed between said surfaces, power driving means interconnected to one of said members and operable to rotate it at a desired speed and thereby driving the other member, pneumatically operated holding and shock absorbing means interconnected to said pulverizing member and supporting means therefor and operable to permit said pulverizing member yieldably to move away from said supporting member to accommodate various thicknesses of the bed of material upon said supporting member while being pulverized, means interconnected to and operable to furnish a supply of pneumatic fluid under pressure to said holding and shock absorbing means, selectively settable control means connected between said supply means and said holding and shock absorbing means and operable to regulate the flow of pneumatic fluid to said latter means to furnish pressure thereto slightly in excess of a desired predetermined operative pressure upon said pulverizing member, and regulating means connected to said control means and operable at a relatively slow rate to maintain the pneumatic fluid pressure upon said holding and shock absorbing means at said lesser desired predetermined operative amount, whereby said pulverizing roller exerts said predetermined pressure upon the material being pulverized regardless of the thickness of the bed thereof upon said supporting member and if sudden movement of said pulverizing member away from said material supporting member occurs, said pneumatic fluid within said holding and shock absorbing means is compressible instantaneously to absorb the sudden increase in pressure in said means by such movement of said pulverizing member.

4. A mill of the continuously pulverizing type comprising in combination, supporting means, a material supporting member rotatably supported by said base for movement about a substantially vertical axis and having a peripheral wall extending upward therefrom to provide an annular dam thereon, power means interconnected to said member to drive it, a casing covering said member and-having inlet means to receive substantially continuously material to be pulverized, an arm mounted exteriorly of said casing and pivoted for movement about a substantially horizontal axis fixed relative to said supporting means, a pulverizing roller within said casing and rotatably supported by said arm for rotation about an axis fixed relative to said arm and disposed within said casing and the peripheral surface of said roller cooperating with one surface of said material supporting member within said dam to pulverize material between said surfaces as said material supporting member is rotated, said pivotal mounting of said arm permitting yielding of said roller toward and from said supporting member during such pulverizing while said pulverizing action progresses, a piston and cylinder unit interconnected to said arm, conduit means connecting said unit to a source of fluid pressure, and control means comprising an adjustable pre-settable pressure valve interconnected to said conduit and fluid bleeding means operable constantly to establish and automatically maintain the fluid pressure in said unit at a predetermined amount and thereby automatically maintain a mean uniform distance between said pulverizing roller and material supporting member for a given condition existing in the mill to process continuously material fed to said member at a substantially uniform rate to maintain a bed of material of substantially uniform depth upon said member during milling operations by said roller to produce a desired range of sizes of pulverized material discharged progressively over said dam.

5. A mill of the continuously pulverizing type comprising in combination, supporting means, a casing extending upward therefrom and having inlet means to receive substantially continuously material to be pulverized, a material supporting member rotatably supported by said base for movement about a substantially vertical axis and having a peripheral wall extending upwardly therefrom to provide an annular dam thereon, power means interconnected to said member to drive it, a pair of arms mounted exteriorly of said casing at opposite sides thereof and respectively pivotally connected to substantially horizontal axes fixed relative to said supporting means exteriorly of said casing, a pulverizing roller rotatably supported within said casing by each arm for rotation about an axis fixed relative to each arm, the peripheral surface of each roller cooperating with circumferentially spaced portions of one surface of said material supporting member with said dam to pulverize material between said surfaces as said material supporting member is rotated, the pivotal mounting of said arms permitting independent yielding of said rollers relative to said supporting member during such pulverizing, a pair of piston and cylinder units disposed on opposite sides of said casing exteriorly thereof and interconnected to said arms, conduit means commonly connecting both said units to a source of fluid pressure, and control means comprising fluid bleeding means, interconnected to said conduit means and operable constantly to establish and automatically maintain the fluid pressure in said unit at a predetermined amount during substantially all positions of said rollers relative to said material supporting member as material is fed thereto at a substantially uniform rate and thereby maintain a bed of material of substantially uniform depth upon said supporting member within said annular dam during milling 17 operations by said roller to produce a desired range of sizes of pulverized material discharged progressively over said dam.

6. A mill of the continuously pulverizing type comprising in combination, supporting means, a casing extending upward therefrom and having inlet means to receive substantially continuously material to be pulverized, a material supporting member rotatably supported within said casing by said base for movement within a substantially horizontal plane about-a substantially vertical axis and having a peripheral wall extending upward therefrom to provide an annular dam thereon, power means interconnected to said member to rotate it, a pulverizing roller within said casing, means supporting said roller for rotation about an axis at an angle to that of said member and said supporting means being movable to vary the peripheral surface of said roller relative to one surface of said material supporting member within said dam to pulverize beds of material of various thicknesses between said surfaces as said material supporting member is rotated, a piston and cylinder unit interconnected to said roller supporting means, conduit means connecting said unit to a source of fluid pressure, control means comprisingfluid bleeding means interconnected to said conduit and operable to establish and automatically maintain the fluid pressure in said unit at a predetermined amount and thereby automatically maintain a mean uniform distance between said pulverizing roller and material supporting member for a given condition existing in the mill to process material fed continuously to said member at a substantially uniform rate to maintain a bed of material of substantially uniform depth upon said member during milling operations by said roller to produce a desired range of sizes of pulverized material discharged progressively over said dam, and means operable to circulate an elastic fluid current upwardly through said casing past said member and roller to entrain pulverized material of a predetermined range of fineness as discharged from said dam and remove the same from said mill.

7. A mill of the continuously pulverizing type comprising in combination, supporting means, a circular material supporting member rotatably supported by said base for movement about a substantially vertical axis and having a peripheral wall extending upward therefrom to pro-' vide an annular dam thereon, means to deliver substantially continuously to said member material to be pulverized, power driving means interconnected to said member, a plurality of arms mounted in peripherally spaced positions around and outside of the perimeter of said member and respectively pivotally connected to substantially horizontal axes fixed relative to said supporting means, a pulverizing roller rotatably supported by each arm for rotation about an axis fixed relative to each arm, the peripheral surface of each roller cooperating with circumferentially spaced portions of one surface of said material supporting member within said dam to pulverize material between said surfaces as said material supporting member is rotated, the pivotal mounting of said arms permitting independent yielding of said rollers relative to said supporting member during such pulverizing, pistons and cylinder units respectively interconnected to said arms, conduit means commonly connecting said units to a source of fluid pressure, and control means comprising fluid bleeding means interconnected to said conduit means and operable automatically to establish and maintain the fluid pressure in said units at a predetermined constant amount regardless of the movement of said rollers away from said member either independently or jointly and thereby condition said mill tov pulverize continuously material fed to said member at a substantially uniform rate to maintain a bed of material of substantially uniform depth upon said member during milling operations by said roller to produce a desired range of sizes of pulverized material discharged progres sively over said dam.

8. A mill of the continuously pulverizing type comprising in combination, a material supporting member rotatable within a substantially horizontal plane about a substantially vertical axis, means to deliver substantially continuously to said member material to be pulverized, power means interconnected to said member and operable to drive it at a desired rate of speed, a pulverizing roller, means supporting said roller rotatably above said member and in position to dispose the peripheral surface of said roller in opposition to the material supporting surface of said member to effect pulverizing of material between said surfaces as said member is rotated, the periphery of said rotatable supporting member being constructed to maintain upon said member a desired depth of material being pulverized and from the periphery of which member pulverized material is discharged progressively, hydraulic pressure holding means comprising fluid bleeding means interconnected to a source of fluid pressure and to said roller supporting means and operable to permit said roller to move away from said member to accommodate variations in the thickness of the material supported upon said member while being pulverized, shock relief means interconnected to said holding means and operable to absorb relatively sudden shock movements of said roller away from said material supporting member, and selectively settable control means interconnected to said pressure holding means and operable to maintain substantially uniform predetermined pressure upon said roller during the pulverizing operation thereof while said pressure holding means exerts continuously substantially the same pressure upon said roller when the same moves away from said member in accordance with variations in thickness of the material upon said material supporting member and said shock absorbing means absorbing momentary shock movements of said roller during operation of said mill.

9. A mill of the continuously pulverizing type comprising in combination, a material supporting member rotatable within a substantially horizontal plane about a substantially vertical axis, means to deliver substantially continuously to said member material to be pulverized, power means interconnected to said member and operable to drive it at a desired rate of speed, a pulverizing roller, means supporting said roller rotatably above said member in position to dispose the peripheral surface of said roller in opposition to the material supporting surface of said member to effect pulverizing of material between said surfaces as said member is rotated, the periphery of said rotatable supporting member being constructed to maintain upon said member a desired depth of material being pulverized and from the periphery of which member pulverized material is discharged progressively, a piston and cylinder unit containing a compressible fluid and interconnected to said roller supporting means, said piston being operable relative to said cylinder to permit said roller to move away from said member to accommodate variations in the thickness of the material supported upon said member while being pulverized, a compression reservoir communicating with said cylinder, a hydraulic pump communicating with said reservoir and operable to pump hydraulic fluid under pressure thereinto and compress said fluid in said cylinder a predetermined amount, a settable regulating valve connected to said reservoir and operable to maintain the hydraulic fluid in said reservoir at a pressure to maintain the desired pressure upon said' piston, and fluid bleeding means'connected to said reservoir, said pressure mechanism serving to hold the roller under substantially constant predetermined pressure during normal mill operation and the pneumatic fluid in said cylinder serving to absorb relatively sudden shock move,-

ments of said roller away from said material supportingmember during such operation.

10. A mill of the continuously pulverizing type com- 19 prising in combination, a material supporting member rotatable within a substantially horizontal plane about a substantially vertical axis', means to deliver substantially continuously to said member material to be pulverized, power means interconnected to said member and operable to drive it at a desired rate of speed, a pulverizing roller rotatably mounted above said member and positioned to dispose the peripheral surface of said roller in opposition to the material supporting surface of said member to effect pulverizing of material between said surfaces as said member is rotated, the periphery of said rotatable supporting member being constructed to maintain upon said member a desired depth of material being pulverized and from the periphery of which member pulverized material is discharged progressively, means a'djustably supporting said roller for movement of the peripheral surface thereof toward and away from said material supporting surface, fluid pressure holding and shock absorbing means interconnected to said roller sup porting means and operable to permit said roller yieldably to move in opposite directions "relative to said member to conform to variations in the thickness of the material supported upon said member while being pulverized, a selectively settable control valve interconnected to said pressure holding and shock absorbing means and operable to maintain substantially uniform predetermined pressure upon said roller during the pulverizing operation thereof, and variably settable valve adjusting means interconnected to said valve and roller supporting means and operable when said roller moves relatively toward or away from said material supporting surface respectively to close or open said valve a greater amount and cause the pressure in said holding and shock absorbing means to vary accordingly a predetermined amount in accordance with the setting of said valve adjusting means.

11. The method of operating a pulverizing mill comprising a material supporting member extending outward from a substantially vertical axis and a pulverizing element rotatably supported above and urged into cooperation with said member by pressure actuated means to operate upon material continuously fed to said member and pulverized between said element and member as the same move relative to each other and pulverized material is discharged from the periphery of saidsupporting mem ber, said method comprising applying fluid under pressure in said means and regulating said pressure upon said pulverizing element while the mill is operating to obtain a desired bed depth of material upon said supporting member and desired angular discharge pattern of said material from the periphery thereof, and sweeping said mill with a fluid current directed upwardly past the periphery of said supporting member and intercepting said angular pattern of material discharged from the periphery of said supporting member to entrain within said current fine material within a predetermined range of sizes to remove the same from coarser particles of the discharged material, said current removing said fine particles from said mill thereby to classify the products of said mill.

The method of operating a pulverizing mill comprising a material supporting member extending outward from a substantially vertical axis and a pulverizing element rotatably supported above and urged into cooperation with said member by pressure actuated means to operate upon material continuously fed to said member and pulverized between said element and member as the same move relative to each other and pulverized material is discharged from the periphery of said supporting member, sard method comprising providing the periphery of said material supporting member with a peripheral wall extending upward therefrom, applying fluid under pressure in said pressure actuated means and regulating said pressure upon said pulverizing element while the mill is operating to obtain a desired bed depth of material upon said supporting member and desired angular discharge pattern of said material from the periphery of said wall upon said supporting member, and sweeping said mill with a fluid current directed upwardly past the periphery of said wall and intersecting the angular pattern of material discharged from the periphery of said wall to entrain within said current fine material within a predetermined range of sizes to remove the same from the coarser particles of the discharged material, said current removing said fine particles from said mill thereby to classify the products of said mill.

13. The method of pulverizing material in a mill irrcluding a material supporting member rotatable within a substantially horizontal plane and a pulverizing roller rotatably mounted above said member and movable toward and away from said member to accommodate material loads or different thickness and urged toward said member by pressure actuated means, said method comprising the steps of starting operation of the mill While pressure on the roller is less than normal operating pressure, progressively feeding material to be ground to said member while the same is rotating, increasing the pressure on the roller and adjusting the feed of material while grinding progresses, and finally adjusting the pressure on the roller to a predetermined substantially constant amount to produce a bed of material of substantially constant thickness which is pulverized progressively 'to a desired range of sizes of pulverized product relative to the rate of feed to the mill and is continuously discharged from said member,

14. The method of pulverizing material 'in a mill including a material supporting member rotatable within a substantially horizontal plane and a pulverizing roller rotatably mounted above said member and movable toward and away from said member to accommodate material loads of different thickness and urgcd toward said member by pressure actuated means, said method comprising the steps of starting operation of the mill while pressure on the roller is less than normal operating pressure, progressively feeding material to be ground to said member while the same is rotating, increasing the pressure onthe roller and adjusting the feed of material as grinding progresses, adjusting the pressure on the roller to a predetermined substantially constant amount to produce a bed of material of substantially constant thickness which is pulverized progressively to a desired range of sizes of pulverized product relative to the rate "of feed to the mill and is continuously discharged from said member, passing an elastic fluid current through said mill past said member and roller, and regulating the velocity of said fluid current in relation to the pulverized material to effect the continuous removal from the mill of a desired range of sizes of fines of said pulverized material and automatically maintaining the pressure on the roller substantially constant irrespective of variations in the thickness of the bed of material being pulverized, thereby rendering the range of pulverized products more uniform.

References Cited in the file of this patent UNITED STATES PATENTS 1,806,980 Kreutzberg May 26, 1931 1,852,435 Ritchie Apr. 5, 1932 1,889,555 King Nov. 29, 1932 1,961,811 Becker June 5, 1934 2,021,895 Newhouse et al Nov. 26, 1935 2,205,632 Schwarz June 25, 1940 2,377,307 Brown June 5, 1945 2,610,802 Mclllvaine Sept. 16, 1952 2,630,975 Horth Mar. 10, 1953 2,684,813 Loesche July 27, 1954 FOREIGN PATENTS 902,573 Germany Jan. 25, 1954 

